What percent of Americans are democrat, republican, independent, & other 3rd party?

Question

& also: What percent of voters?

Answer 1

About 43% are registered as Democrats, about 33% are registered as Republicans, the Green, Libertarian, and Constitution Parties all have about 1% of the population as registered members, and about 21% are unaffiliated.  

While I have never seen a study to prove this, there are generally assumed to about twice as many conservative independents as there are liberal independents.  I have to assume this is why democrats' registration numbers are higher.